Water-thrifty <B>Agastache rupestris</B>, commonly known as "Sunset" hyssop or licorice mint, thrives in a xeric garden near a commercial strip in Lafayette.

"Blue Fortune," a European hybrid hyssop, grows as tall as 36 inches, with blooms in powder blue. Leaves are large and green with a silvery underside. The plant needs some water and is hardy to Zone 4.

Like many tales of the West, how the agastache, or hummingbird mint, grew from a niche plant of the Arizona and New Mexico hills to one of the best- loved and most-requested landscape plants of the Rocky Mountain region, depends on whom you talk to.

• A program called Plant Select that sprang up to test, choose and market great performers for Colorado’s climate;

• A few dedicated, even obsessed plant breeders;

• Hummingbirds, which pollinate — and more important, cross-pollinate, the plants;

• A years-long drought just as a growing population forced a focus on water-sipping plants.

The story adds a new chapter every growing season, in species and cultivars that include new introductions in a rainbow of colors, heights from dwarf to 5 feet, and cold hardiness up to Zone 4.

Agastache’s story begins with a cultivar called “Sunset” hyssop — Agastache rupestris, a coral- and-lavender blooming plant, hybridized from wild collected seed in the late ’90s and now sold at most garden centers in the West.

“They’re wonderful along a walkway where you brush up against them,” says Debbie Wedlake, who sells several types of fragrant agastaches at Tagawa Gardens in Centennial. “We have hummingbirds who come into the garden just for the aga- stache.”

Jim Klett, a Colorado State University professor and landscape horticulturist, says it’s not exaggeration to call “Sunset” hyssop a flower that’s won the West.

Plant Select, a joint CSU Extension-Denver Botanic Gardens program, chooses only five or six plants a year. It picked “Sunset” Agastache rupestris in 1997 — the program’s first year.

“It’s been a real success story,” Klett says. Since then, “Sunset” has become a common thread in a lot of gardens, including at the Denver Zoo and Invesco Field at Mile High (it’s not too big a stretch to say the plant blooms in Denver Broncos orange and blue).

Pride rings in Klett’s voice when he talks about Agastache rupestris. “It’s been real gratifying for those of us who’ve been pioneers with this program to see it planted all up and down the Front Range,” he says.

Chapter 2 belongs to the plant geeks.

“I’m kind of fanatical for growing things from seed,” admits Joy Andrews, who has developed several agastaches in her backyard garden in southeast Fort Collins. “So I collected a bunch of seeds from Agastache rupestris.”

Agastaches grown from seed can — and often do — hybridize enthusiastically, showing infinite genetic variability, while those grown from cuttings are clones, remaining identical to their parents.

Andrews planted seeds around the yard, and waited. “The third year, one had huge blooms — a good 5 inches across, held on a much larger flower cluster.” At that point she dug the plant and reproduced it from cuttings.

She called her new creation “Joyful,” and has sold it from her house and at Fort Collins Nursery, where she works. It seems to have one of the longer life spans among agastaches, sticking around as long as five years, she says.

The variety also attracted the attention of Plant Select and now is on track for the program’s 2010 selections.

Andrews says the program also is evaluating a yellow agastache that she produced, to be called “Coronado Sunrise.” And she’s working on a third she plans to call “Hummer’s Joy.”

She’ll sell her agastaches from her house this spring when they’re ready, and says interested gardeners should watch the farm and garden listings on Craigslist.

David Salman, owner of High Country Gardens in Santa Fe, sells a dozen varieties of agastaches and is always pushing the plant’s genetic envelope. Eventually, he found one — a plant with blooms of pink and deep, dark, raspberry — that he thought was special enough to name it after his wife, Ava.

But no pressure.

“I knew it had to be good,” he says with a laugh when asked what kind of a performer a plant would have to be to bear that kind of responsibility.

So when a volunteer agastache showed up that he thought might be something special, he watched it for five years. It proved special beyond his dreams.

“It’s a fantastic and distinctive plant,” he says. “It has a very long bloom time, at least three months, depending on when the first hard frost is. It’s also unique in that there are two parts to the agastache’s flower, and the calyx on ‘Ava’ — the part that flower pushes out of, stays dark rose- pink even after the flower has finished blooming.”

On the vivid-colored horizon for High Country? Salman has great hopes for a cultivar of Agastache cana that he’s now selling called “Rosita”; it’s distinguished by its semi-dwarf habit. He’s also working on “a real good cold-hardy blue,” though he likes his current one, “Blue Fortune.”

For home gardeners, now isn’t the best time to view agastaches. They come into their glory in mid- to late summer, then carry the garden into fall’s epilogue.

But as summer bears down, agastaches bear up.

“They’re very adaptable and easy to grow in dryer gardens,” says Dan Johnson, curator of native plants at the Denver Botanic Gardens.

“I think they tend to be nice and vigorous and full; they bloom for a long time and add a different shade to the color palette.”

Visitors to the gardens can see agastaches blooming around the lobby entrance, in the water garden and rock garden, and scattered all around, Johnson says.

But if they’re hoping to feast their eyes on agastaches’ most celebrated fans — hummingbirds — he recommends visiting in August and September, when the agastaches are in peak bloom. The birds usually make a brief stop at the gardens in May, but then spend a few months in the foothills before a final summer feast.